By Ian Simpson


WASHINGTON (Reuters) - Potentially dangerous electrical arcing in Washington's Metro, the second-busiest U.S. subway system, has increased, federal investigators said in a report on Friday, just weeks before an expected flood of visitors for Donald Trump's presidential inauguration.


Inspections of deteriorating power cables forced a shutdown of the Metro in March, throwing the system into chaos. Electrical arcing, which can burn cables and track parts, was the cause of a fatal fire in early 2015.


The report, by Federal Transit Administration (FTA), said that Metro, which carries about 700,000 passengers daily, had 70 incidents of electrical arcing since the agency's unprecedented takeover of safety oversight in October 2015.


All of them prompted an emergency response such as station shutdowns or train evacuations, the report said. The rate of arcing incidents was more than twice that experienced from 2012 to 2015, although there has been an improvement since June, the report said.


In a statement, the Metro said it had been working on track power problems for more than a year and its findings had been used in the report.

"Metro will continue to work collaboratively with FTA to address findings and further improve safety," it said.

The report cited a history of deteriorating parts, lack of maintenance, shortage of mechanics and safety lapses, such as power cablescovered with mud and water. The FTA ordered the Metro to carry out almost four dozen fixes to the system.

The subway system is facing falling numbers of riders, a $290 million budget gap and job cuts. Agency officials say Trump's vow to spend $1 trillion on infrastructure nationwide could be a lifeline.

The Metro carries tens of thousands of federal employees daily and is expected to transport many of the million visitors forecast for Trump's Jan. 20 inauguration.

(Reporting by Ian Simpson; Editing by Grant McCool and Steve Orlofsky)